By Claire WhitakerWhen you run a portable air purifier, the fan speed directly affects both how much air gets cleaned and how much sound the unit makes. The U.S. Environmental Protection Agency (EPA) explains that higher fan speeds and longer run times increase the amount of air filtered, and that noise levels depend in part on the fan speed setting. ENERGY STAR adds that larger models use more energy. This guide explains what to compare so you can balance clean air with a comfortable living space.
Noise ratings are reported for some portable air cleaners, according to the EPA’s Guide to Air Cleaners in the Home. The rating may be shown on the product packaging, and noise levels depend in part on the fan speed setting. If noise might prevent you from running the unit, the EPA suggests considering an air cleaner that has a low published noise rating. For reference, a noise rating around 50 decibels (dB) is roughly the operating noise of a modern refrigerator. The University of Washington Environmental Health & Safety (EH&S) department recommends units under 50 dB because higher sound levels may interfere with concentration or cause annoyance.
Energy use is another factor tied to fan speed. ENERGY STAR states that a standard room air cleaner, operating continuously, uses approximately 394 kWh per year in electricity, which is more than the energy used by some new refrigerators. ENERGY STAR certified room air cleaners are more than 50% more energy-efficient than standard models, saving consumers about 211 kWh per year, with the savings depending on the size of the unit. The ENERGY STAR label means the unit meets strict energy efficiency guidelines set by the EPA, but the label does not refer to air-cleaning effectiveness in any way, as noted in the EPA guide.
Clean Air Delivery Rate and Its Effect on Noise and Energy
Most portable air cleaners are rated according to their clean air delivery rate (CADR), a number that helps consumers select an air cleaner based on the size of the area it will be placed in. The EPA guide explains that the higher the CADR, the more particles the air cleaner can filter and the larger the area it can serve. The rating is typically measured at the air cleaner’s highest speed. To filter particles effectively, choose a portable air cleaner that has a CADR large enough for the room or area where you will use it. The EPA provides a sizing chart for estimation purposes, based on an 8-foot ceiling. If you have higher ceilings, you may want to select a portable air cleaner with a higher CADR.
ENERGY STAR says larger models use more energy, so it advises choosing a model sized for the room. Its specification for room air cleaners measures energy efficiency using the Integrated Energy Factor (IEF), which uses a Clean Air Delivery Rate-to-Watt ratio. In other words, the program rates efficiency by how much clean air a unit delivers for each watt it uses. For a deeper look at sizing, see our guide on sizing an air purifier to your room.
Comparing Noise, Energy, and Filtration Factors
The table below summarizes the key factors to compare when evaluating an air purifier’s noise and energy performance, based on information from the EPA and ENERGY STAR.
| Factor | What to Know | Source |
|---|---|---|
| Noise level and fan speed | Noise ratings are reported for some portable air cleaners; levels depend on fan speed. A rating around 50 dB is similar to a modern refrigerator. Higher fan speeds increase filtration but also noise. | EPA Guide to Air Cleaners in the Home; UW EH&S |
| Energy use and ENERGY STAR | Standard units use about 394 kWh/year. ENERGY STAR certified models are more than 50% more efficient, saving about 211 kWh/year. | ENERGY STAR |
| CADR and room size | Higher CADR filters more air and serves larger rooms, but the rating is measured at the highest speed. Match CADR to room square footage using the EPA sizing chart. | EPA Guide |
| Fan speed and run time | Higher fan speeds and longer run times increase air filtration; noise depends in part on fan speed. An air cleaner filters less air at lower speeds. | EPA Guide |
| Filter type and maintenance | HEPA filters help achieve high CADR for particles. Activated carbon filters can remove gases but have no widely used performance rating. All filters need regular replacement; a dirty filter won’t work well. | EPA Guide |
Placement and Its Impact on Performance
Where you put the air purifier affects how well it works and how you perceive its noise. The EPA guide recommends placing the unit in the room or rooms where you spend the most time. Many units are designed to sit on the floor, while some are made for tabletops. Either way, make sure the airflow is not obstructed. Keep air cleaners away from curtains and anything that might block airflow. If the air cleaner causes an uncomfortable draft, redirect the airflow away from you. The University of Washington EH&S adds that for best performance, you should place the unit near the center of the room when practical, while maintaining clearance around the air intake and not blocking walkways. For more placement tips, read our air purifier placement guide.
Filter Maintenance and Long-Term Costs
All filters need regular replacement. The EPA guide states that if a filter is dirty and overloaded, it won’t work well. Manufacturers typically recommend replacement every 60 to 90 days, though many factors can affect how quickly filters get dirty. If filters appear heavily soiled when you replace them, you should consider changing them more frequently. The University of Washington EH&S advises buying replacement filters when you purchase the air cleaner, and when changing filters, avoid shaking or disturbing dust on the old filter. Place it directly in a plastic garbage bag and seal it tightly before disposal. Learn more about the different filter types in our air purifier filter types guide and see our air purifier maintenance article for a full care routine.
What to Avoid
The EPA guide warns against portable air cleaners that intentionally produce ozone, because ozone is a lung irritant. Some air cleaners that contain electrostatic precipitators, ionizers, UV lights without adequate lamp coatings, and plasma air cleaners may have the potential to emit ozone. Both the California Air Resources Board and the Association of Home Appliance Manufacturers maintain lists of air cleaners that have been checked and shown to emit little or no ozone. The EPA also notes that portable air cleaners and HVAC filters do not address the cause of mold and musty odors, which is a water or moisture problem.
The most effective ways to improve indoor air are to reduce or remove the sources of pollutants and to ventilate with clean outdoor air, as the EPA guide emphasizes. Filtration is a supplement, not a substitute.
Frequently asked questions
Do all air purifiers have a noise rating?
Noise ratings are reported for some portable air cleaners, according to the EPA. The rating may be shown on the product packaging, and it typically varies with the fan speed setting. If noise is a concern, look for a unit with a low published noise rating.
Does a higher CADR always mean more noise?
Not necessarily, but the CADR rating is usually measured at the air cleaner’s highest speed, which is often the loudest setting. The EPA guide notes that an air cleaner will filter less air if it is set at a lower speed.
Can an ENERGY STAR air purifier still be loud?
Yes. The ENERGY STAR label means the unit meets energy efficiency guidelines set by the EPA, but the EPA guide says the label does not refer to air-cleaning effectiveness in any way. Check the packaging separately for a noise rating, which the EPA says some units report.
For more on choosing and using an air purifier, browse our air purifier guides.
Sources
- ENERGY STAR: Air Cleaners
- EPA: Guide to Air Cleaners in the Home (2nd edition, PDF)
- EPA: Guide to Air Cleaners in the Home (web page)
- University of Washington EH&S: Portable Air Cleaners and Household Fans
About Claire Whitaker
Claire Whitaker is part of our editorial team and reviews and edits our non-vacuum cleaning gear guides, checking product details against manufacturer specifications and owner feedback.
